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      <p>
        Many disk drives contain onboard caches. Some of these
        drives include battery-backup or other functionality that
        guarantees that all cached data will be completely written if
        the power fails. These drives can offer substantial
        performance improvements over drives without caching support.
        However, some caching drives rely on capacitors or other
        mechanisms that guarantee only that the write of the current
        sector will complete. These drives can endanger your database
        and potentially cause corruption of your data.
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        To avoid losing your data, make sure the caching on your
        disk drives is properly configured so the drive will never
        report that data has been written unless the data is
        guaranteed to be written in the face of a power failure. Many
        times, this means that write-caching on the disk drive must be
        disabled.
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